Schimbul de mingi se termină cu un punct.

Because -ul is the Romanian definite article attached to a masculine/neuter singular noun.

• schimb = exchange
• schimbul = the exchange

So schimbul de mingi means the ball exchange or, more naturally in sports English, the rally.

de often means of in Romanian, especially in noun combinations.

So:

• schimbul de mingi = literally the exchange of balls

In sports language, this refers to the back-and-forth hitting sequence, so the natural English meaning is the rally.

This structure is very common in Romanian:

• pahar de apă = glass of water
• teren de tenis = tennis court
• schimb de replici = exchange of remarks

The singular is minge = ball.

The plural is mingi = balls.

In the phrase schimb de mingi, Romanian uses the plural because it refers to the repeated back-and-forth action involving the ball in play. Even though in many sports there is physically one ball, this expression is idiomatic and standard.

So:

• minge = one ball
• mingi = balls

Because a se termina means to end / to come to an end, while a termina usually means to finish something.

Compare:

• Meciul se termină. = The match ends.
• Jucătorul termină meciul. = The player finishes the match.

So in your sentence, schimbul de mingi se termină means the rally ends or the rally comes to an end.

The se here is part of the verb’s normal form in this meaning. It is not translated word-for-word as itself.

Because the subject is schimbul, not mingi.

The structure is:

• Schimbul = the subject
• de mingi = a descriptive phrase modifying schimbul

So the verb agrees with schimbul, which is singular:

• Schimbul ... se termină = The rally ... ends

This is similar to English:

• The exchange of balls ends not
• The exchange of balls end

It is present tense, third person singular.

The verb is a se termina.

Present tense:

• eu mă termin = I end / I get finished
• tu te termini
• el/ea se termină
• noi ne terminăm
• voi vă terminați
• ei/ele se termină

In this sentence, the present tense can describe:

• a general rule
• a habitual action
• a commentary-style action in sports

So it can mean something like A rally ends with a point.

cu usually means with.

So literally:

• se termină cu un punct = ends with a point

In natural English, this may also be understood as:

• ends in a point
• ends when a point is scored

Romanian often uses cu in this kind of result expression:

• povestea se termină cu o surpriză = the story ends with a surprise
• discuția s-a terminat cu o ceartă = the discussion ended with an argument

Because un punct means a point, not the point.

Here the sentence is stating what happens in general: the rally ends with a point being scored. It is not talking about one specific previously mentioned point.

Compare:

• cu un punct = with a point
• cu punctul = with the point / with that specific point

In most general statements like this, Romanian uses the indefinite form.

Yes. It is a normal and understandable expression in sports contexts, especially for tennis, table tennis, volleyball commentary, and similar situations where there is a back-and-forth play.

Depending on the sport and style, Romanian might also use more specialized wording, but schimbul de mingi is perfectly natural and transparent.

A learner should recognize it as a sports phrase meaning rally or exchange of shots/hits.

A rough pronunciation guide is:

SKIM-bul de MINGY se ter-MI-nuh ku oon punkt

A few useful details:

• sch in schimbul sounds like English sh in ship
• gi in mingi sounds roughly like the end of orange or jeep, depending on accent and context; here it is a soft sound
• ă in termină is the Romanian ă, a short neutral vowel, similar to the a in sofa
• ț would sound like ts, but there is no ț in this sentence
• Romanian stress here is:
  • SCHIMbul
  • MINgi
  • terMI-nă
  • PUNCT

Yes, Romanian word order is somewhat flexible, but the given sentence is the most neutral and natural order.

Standard order:

• Schimbul de mingi se termină cu un punct.

You might sometimes hear variations for emphasis, but they are less neutral. For a learner, the given order is the best one to use.

It follows a very common Romanian pattern:

subject + verb + complement

So it is a good model sentence to remember.